Waste materials which are pyrophoric, water-reactive, or both must be deactivated before they can be turned over to waste handlers for disposal. Of particular concern herein is waste products derived from the production of dimethylaluminum hydride (Me.sub.2 AlH) or dimethylgallium hydride (Me.sub.2 GaH). In particular, this invention is directed to deactivation of wastes containing compounds of the formula Li(MH.sub.3 R) where M is Al or Ga and R is a low molecular weight hydrocarbon radical or a halogen.
One common method for deactivation of water-reactive substances is reaction with a weak proton donor, e.g., an alcohol, such as isopropanol. Reaction of Li(MH.sub.3 R) compounds with weak proton donors produce gels which are difficult to handle, e.g., difficult to remove from their reaction vessels. Removal of deactivation products of Li(MH.sub.3 R) compounds from reaction flasks is of significant concern because it is frequently necessary to deactivate such compounds directly in their reaction flasks. Although Li(MH.sub.3 R) compounds are not necessarily pyrophoric, Li(MH.sub.3 R)-containing waste products often contain additional pyrophoric wastes which must be maintained under an inert atmosphere prior to deactivation.
It is known to produce dimethyl aluminum hydride by reaction of trimethyl aluminum with lithium aluminum hydride (LAH): EQU Al(CH.sub.3).sub.3 +LiAlH.sub.4 .fwdarw.(CH.sub.3).sub.2 AlH+LiAlH.sub.3 CH.sub.3.
or by a procedure described in U.S. patent application Ser. No. 07/136,032, which describes the reaction of waste products or residues of trimethylgallium production [(CH.sub.3).sub.2 AlCl, (CH.sub.3).sub.3 Ga and (CH.sub.3).sub.3 Al] with lithium aluminum hydride to produce product dimethylaluminum hydride. EQU (CH.sub.3).sub.2 AlCl+LiAlH.sub.4 .fwdarw.(CH.sub.3).sub.2 AlH+LiAlH.sub.3 Cl EQU (CH.sub.3).sub.3 Ga+LiAlH.sub.4 .fwdarw.(CH.sub.3).sub.2 AlH+LiGaH.sub.3 CH.sub.3
This application, in background, describes how the waste products of trimethylgallium production were deactivated either by reaction with ethyl alcohol or reaction with ethyl acetate in heptane.
The major waste product of the reaction of trimethylaluminum and LAH is lithiummethyltrihydridoaluminate (LiAlH.sub.3 CH.sub.3), which is water reactive (though in itself not particularly pyrophoric). However, after distillation of product dimethylaluminum hydride, some dimethylaluminum hydride (CH.sub.3).sub.2 AlH, which is pyrophoric, trimethylaluminum (CH.sub.3).sub.3 Al, (TMA) which is also pyrophoric and LAH, which is not pyrophoric, remain. Deactivation of the major product, lithiummethyltrihydridoaluminate, is a major concern; however, the presence of the pyrophoric compounds requires that the major product be deactivated under an inert atmosphere, such as N.sub.2. This generally requires that the deactivation take place in the reaction vessel itself. Naturally, it is highly desirable that the deactivation products be removable from the reaction vessel. Neither of the deactivation methods referenced in U.S. patent application 07/136,032 are suitable for the residues of the reaction of TMA and LAH. Isopropyl alcohol produces a gelled product. Reaction of the residues with ethyl acetate in heptane would produce insoluble products which could not easily be removed from the reaction flask.
If instead of reacting LAH with pure TMA, the LAH is reacted with the waste products of trimethyl gallium production, the major waste product is lithiumchlorotrihydroaluminate (LiAlH.sub.3 Cl) admixed with pyrophoric residual products. Similar deactivation problems are presented.